Catalytic performance of a boron peroxotungstate complex under homogeneous and heterogeneous conditions

authors	Santos, ICMS; Balula, SS; Simoes, MMQ; Cunha-Silva, L; Neves, MGPMS; de Castro, B; Cavaleiro, AMV; Cavaleiro, JAS
nationality	International
journal	CATALYSIS TODAY
author keywords	Boron; Peroxotungstate; Oxidation; Hydrogen peroxide; Heterogeneous; Catalysis
keywords	HYDROGEN-PEROXIDE; SELECTIVE OXIDATION; ALLYLIC ALCOHOLS; DINUCLEAR PEROXOTUNGSTATE; MODIFIED SILICA; EPOXIDATION; MONOTERPENES; TUNGSTEN; OLEFINS; H2O2
abstract	The preparation and characterization (FT-IR, FT-Raman, B-11 MAS NMR, diffuse reflectance, elemental analysis) of a novel boron peroxotungstate (BTBA)(4)H[BW4O24] (BTBA = benzyltributylammonium) is reported, along with its use in the homogeneous oxidation of cis-cyclooctene, geraniol, linalool and (-)-carveol with H2O2 as oxidant and acetonitrile as solvent. High catalytic activity was registered for all the substrates studied under homogeneous conditions, namely 99% of conversion of geraniol after 2 h, 93% for linalool after 5 h, 74% for cis-cyclooctene after 6 h, and 100% for (-)-carveol after 2 h of reaction. Some oxidation studies were carried out with the Venturello complex, [PW4O24](3-), in the same conditions. Furthermore, the boron peroxotungstate (BW4) was immobilized using two different strategies: (a) BW4 anchored into a functionalized silica (aptesSiO(2)) giving BW4@aptesSiO(2) and (b) BW4 encapsulated on a metal organic framework, commonly referred as MIL-101, giving BW4@MIL-101. The catalytic activity of both heterogeneous materials was investigated for geraniol oxidation and the results were compared with those obtained with BW4 under homogeneous conditions. The encapsulated boron peroxotungstate (BW4@MIL-101) gave rise to the best results, reaching complete conversion of geraniol after 3 h of reaction and 78% selectivity for 2,3-epoxygeraniol. Additionally, this heterogeneous catalyst could be reused without appreciable loss of catalytic activity, affording similar 2,3-epoxygeraniol selectivity. The heterogeneous catalysts' stability was also investigated after the oxidation reactions by different characterization techniques. (C) 2012 Elsevier B. V. All rights reserved.
publisher	ELSEVIER SCIENCE BV
issn	0920-5861
year published	2013
volume	203
beginning page	87
ending page	94
digital object identifier (doi)	10.1016/j.cattod.2012.03.071
web of science category	Chemistry, Applied; Chemistry, Physical; Engineering, Chemical
subject category	Chemistry; Engineering
unique article identifier	WOS:000314825300014